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A T Nguyen

Publications and source records attributed to A T Nguyen.

66 records · Page 4Linked to original sources
PubMed1988

Macrophage oxidative activation potential in normal and endotoxin-treated Biozzi high and low antibody responder mice.

The present study is an attempt to verify the hypothesis that high (HI) and low (LI) antibody responder Biozzi mice, which differ strikingly in their macrophage capacities to catabolize antigens and to exert bactericidal activity (the LI being more potent than the HI line), demonstrate a similar genetic disparity in their macrophage oxidative metabolism activation potential. The production of reactive oxygen intermediates was measured by luminol-dependent chemiluminescence in cell suspensions from various sources including: bone marrow, peripheral blood, spleen, peritoneal exudate, thymus, and mesenteric lymph nodes. Chemiluminescence was determined both in the absence and presence of particulate (opsonized zymosan and latex) and soluble (phorbol myristate acetate and concanavalin A) membrane-stimulating agents. Lastly this investigation was conducted both in normal and endotoxin (lipopolysaccharide from Escherichia coli) treated HI and LI mice in an attempt to unmask the hypothesized difference by increasing the macrophage oxidative response capacity. Results obtained did not show the expected interline differences in reactive oxygen intermediate production regardless of cell origin, stimulating agent or lipopolysaccharide in vivo treatment. On the other hand, the well-documented enhancing effect of lipopolysaccharide on macrophage oxidative metabolism depended on the origin of the cell suspension. Indeed, it was not observed in bone marrow and peripheral blood from either HI or LI mice, was clearly demonstrated in the spleen and peritoneal exudate from both mouse lines, and surprisingly, in the thymus and lymph nodes from HI but not LI mice.

Animals↗
PubMed1985

Chemiluminescence monitoring of phagocyte oxidative metabolism in mice bearing polyacrylamide induced granulomas.

A technical protocol was recently described by Fauve et al. (J. Immunol. Methods 1983, 64, 345) for inducing subcutaneous granuloma with polyacrylamide microbeads. The present study using this technique demonstrates that the capacity of host phagocytes to generate reactive oxygen species can be easily monitored by chemiluminescence, both locally in granuloma infiltrating cells and at sites remote from the inflammatory reaction, i.e., within microamounts of whole blood and in spleen cells. We observed that both resting and stimulated (zymosan or phorbol-myristate acetate) production by C57BL/6 mouse phagocytes are significantly higher in granulomas induced with high porosity polyacrylamide beads (P300) than in those induced with beads of low polyacrylamide porosity (P4). Since this selective modulation of phagocyte oxidative metabolism is also detectable within microamounts of whole blood and in spleen cells, it could serve as a model for investigating the role of reactive oxygen species in the inflammatory reaction.

Acrylic Resins↗
PubMed1985

Hemodialysis membrane-induced activation of phagocyte oxidative metabolism detected in vivo and in vitro within microamounts of whole blood.

The production of reactive oxygen species by phagocytes from uremic patients undergoing hemodialysis was monitored by chemiluminescence (CL) within microamounts of whole blood or isolated polymorphonuclear (PMN) cells, and compared on the basis of the dialysis membrane, cuprophane (CUP) or polyacrilonitrile (PAN). Compared to control subjects, resting and stimulated CL (with latex, zymosan, phorbol myristate acetate (PMA) but not formyl-methionyl-leucyl-phenylalanine (FMLP) were decreased in 10(-2) diluted blood sampled before dialysis. After 15 min of dialysis (ti), resting whole blood (10(-1) and 10(-2) diluted) CL increased sharply in patients dialyzed with the CUP but not the PAN membrane, while it returned to its predialysis level at the end of the session. This sharp resting CL increase found in whole blood at ti was not observed in isolated PMN cells except when tested with ti plasma from CUP dialyzed patients, suggesting that it was mediated via activated plasma compounds. In vitro treatment of normal blood, plasma, and isolated PMN cells with CUP membrane fragments reproduced this in vivo dialysis-induced activation of phagocyte oxidative metabolism strikingly and demonstrated additionally the requirement of complement for its induction. We propose this model as an effective means of evaluating dialysis membrane biocompatibility.

Acrylic Resins↗
PubMed1984

[Activation of oxidative metabolism of granulocytes and monocytes by IGG-coated platelets from patients with thrombocytopenia].

We have previously shown that monoclonal anti-T cell antibodies bound to their specific targets can trigger the activation of monocyte/macrophage oxidative metabolism through an Fc receptor-mediated interaction. The present study demonstrates that IgG coated platelets from patients with thrombocytopenia-associated diseases can induce a similar respiratory burst activation in polymorphonuclear and mononuclear phagocytes from normal individuals. The intensity of the oxidative reaction as measured by luminol-dependent chemiluminescence is in close correlation with the level of surface-bound IgG molecules as determined by a radioactive anti-immunoglobulin assay. This new methodology to evaluating IgG fixed on human platelets by their capacity to trigger the generation of highly reactive oxygen species by granulocytes and monocytes has also suggested a new mechanism in the genesis of thrombocytopenia associated with autoimmune diseases.

Cell Membrane↗
PubMed1984

Effect of LPS on the oxidative metabolism of peritoneal and spleen cells from LPS sensitive and resistant mice.

The influence of LPS on peritoneal and spleen cell oxidative metabolism was investigated in LPS sensitive (C57BL/6) and LPS resistant (C3H/HeJ) mice following intraperitoneal or subcutaneous injection, by measurement of chemiluminescent (CL) responses to latex particles. In C57BL/6 mice, LPS induced a marked increase in peritoneal and spleen cell CL responses, regardless of the route of injection. On the 2nd day, the effect of LPS on peritoneal cells could be fully explained by an inflammatory reaction, while on the 4th day it could be related to an "activated state" of peritoneal macrophages. In contrast, such an in vivo effect of LPS in peritoneal or spleen cell CL responses was not found in C3H/HeJ mice except on the 2nd day following the injection and with the highest LPS dosage and could be totally due to the LPS induced inflammatory reaction. In vitro studies showed that extremely low concentration of LPS increased CL response capacities of C57BL/6 spleen cell to latex particles. In contrast, CL responses from C3H/HeJ spleen cells remained unaffected by LPS except when submitted to concentrations which proved toxic for the sensitive strain CL producing cells. These results lend additional evidence for the involvement of reactive oxygen species (ROS) in the metabolic consequences of LPS-induced macrophage activation.

Animals↗
PubMed1983

Monoclonal antibodies against T cell differentiation antigens initiate stimulation of monocyte/macrophage oxidative metabolism.

Within the first minute after incubation with the mouse anti-human T cell orthoclone monoclonal antibodies OKT3, OKT4, and OKT8, and in the absence of complement, human monocytes generate a burst of highly reactive oxygen metabolites as detected by a luminol-dependent photometric chemiluminescence (CL) assay. The kinetics of the CL responses to these antibodies are identical to that induced by OKM1, the monoclonal antibody to human monocytes and granulocytes. With regard to CL response intensities, OKM1 induces the maximal response and those of OKT3, OKT4, and OKT8 closely reflect the proportion of T cell subsets recognized by these antibodies in peripheral blood. This reaction is also observed when monoclonal antibodies against mouse Lyt surface determinants (Lyt-1 and Lyt-2) and Thy-1 antigen are tested against murine spleen cells. This murine model was further used to investigate the specificity and the mechanism of this reaction. It was demonstrated that the CL response is Lyt antigen specific, occurs upon addition of monoclonal IgG but not IgM antibodies, requires the concomitant presence of CL-producing cells (CLPC) (promonocytes, monocytes, macrophages, and/or granulocytes) and of fully differentiated T cells, and lastly, is mediated via a T cell opsonization process. Selective blockade of bone marrow cell Fc receptors (FcR II) with monoclonal anti-mouse FcR II antibody inhibits the CL response to IgG2b anti-T cell antibody-coated thymocytes and thus strongly suggests that the stimulation of CLPC oxidative metabolism in this model results from the binding of opsonized T cells to plasma membrane Fc receptors. These observations lend additional support to increasing evidence that the initiation of effector functions by monoclonal anti-T cell antibodies may be strictly dependent upon the presence of monocytes and/or macrophages.

Animals↗
PubMed1983

Modulation of human granulocyte and monocyte chemiluminescence responses: evidence for distinct free radical generating systems.

Using a previously described luminol-dependent photometric chemiluminescence (CL) assay we have investigated the relative significance of the free radicals in the CL phenomenon associated with the respiratory burst of granulocytes and monocytes. The O-2 scavenger, superoxide dismutase, quenches approximately 50% of CL emission from resting and stimulated cells of both types. CL production from granulocytes and monocytes, in the presence of catalase, indicates that H2O2 plays a much less significant role in monocyte light emission than in that of granulocytes. Sodium azide, an 1O2 scavenger and potent inhibitor of peroxidase, and sodium benzoate, an OH. scavenger, both induced 90% reductions of light output from both cell types in resting or stimulated states. The distinct effects of cytochalasins on granulocytes and monocytes further suggest distinct CL generating mechanisms for each cell type. No difference was observed between granulocyte and monocyte CL response in chronic granulomatous disease (CGD) and other clinically related but unknown phagocyte metabolic disorders, whereas selective CL response abnormalities were observed in patients with severe isolated phagocyte chemotaxis defects.

Concanavalin A↗
PubMedDate not supplied

Chemiluminescence in microamounts of whole blood for investigation of the human phagocyte oxidative metabolism function.

The present study was undertaken in order to investigate more precisely the chemiluminescence (CL) phenomenon and thus the generation of oxygen-free radical products by polymorphonuclear granulocytes (PMN) and monocytes (MN) as takes place in whole blood. A luminol-dependent photometric assay previously devised in our laboratory was used to simultaneously evaluate the CL production by resting cells and cells stimulated by a series of particulate and soluble surface-stimulating agents: latex particles, opsonized zymosan, phorbolmyristate acetate and concanavalin A. In order to quantify the overall light-quenching effect of blood on light emission and subsequently to determine the actual CL output by PMN and MN present in whole blood, Pholad luciferin was used as a constant source of light. This approach allowed the observation that CL production by cells in whole blood was of a much higher order than that of isolated cells. Application of this CL assay to investigate oxygen-free radical production in patients suffering from chronic granulomatous disease and related phagocytic cell disorders permitted the early and accurate diagnosis of such genetic disorders. Of great interest were the preliminary results obtained in patients with inflammatory diseases showing a marked discrepancy between background CL emission from whole blood and isolated cells. In conclusion, this investigation of PMN and MN oxidative metabolism in whole blood allows for the precise evaluation of CL production by phagocytic cells in an in vitro situation which closely mirrors their in vivo environment. Such advantages encourage its widespread application in both human and experimental physiopathology in order to further elucidate the in vivo role of oxygen-free radicals in the mechanisms of host resistance against pathogens.

Adult↗
PubMedDate not supplied

Renal Na+, K+-ATPase in SHR: studies of activity and gene expression.

The mechanism by which increased dietary intake of calcium reduces blood pressure in the spontaneously hypertensive rat is unknown. The present studies were designed to determine if there were alterations in the activity of the major membrane ion translocating pump, sodium, potassium-ATPase (NKA), in the kidneys of hypertensive rats and whether increased dietary calcium intake affected the activity of this enzyme. Fifteen-week old SHR's were found to have lower total ATPase activity in microsomal preparations from the kidney than age matched Wistar-Kyoto animals. Both the ouabain-sensitive component (NKA) and the ouabain-insensitive component were lower in SHR. Increasing dietary calcium intake from 1% to 3% elevated both components of the ATPase activity in SHR, but was without effect in WKY. Measurement of membrane phospholipid composition suggested that altered phospholipid composition did not account for the reduced ATPase activity observed, but indicated a reduced density of ATPase in SHR. A technique has been devised for qualitative and quantitative analysis of Na, K-ATPase alpha isoforms using RT-PCR. This technique reveals that the alpha 1 isoform is the sole catalytic isoform present in the nephron. Accurate and precise quantification of the amount of gene expression in individual nephron segments is reported and will be applied to determine whether dietary calcium influences blood pressure by a mechanism which alters nephron NKA gene expression.

Animals↗
PubMedDate not supplied

Flash detection of anti-H-2 antibodies using chemiluminescence, without complement.

Within the first minute following their exposure to a specific anti-H-2 serum and in the absence of complement, murine spleen cells generate a chemiluminescence phenomenon which is precisely measurable by photometry in the presence of luminol. The reaction lasts approximately 10 to 20 minutes, it also generated by bone marrow and, although weakly, by peritoneal cells. In contrast, thymus cells remain totally unresponsive. The striking inhibition of the phenomenon in the presence of superoxide dismutase confirmed that it is indeed due to O2(-). This rapid, simple, inexpensive, extremely sensitive and reproducible technique offers the advantage of focusing on the histocompatibility antigens borne by monocytes, macrophages and granulocytes. Lastly, this O2(-) production triggered by anti-H-2 antibodies should be kept in mind when discussing the mechanism of vascular damage in allograft rejection.

Animals↗